
function Hv=H(alpha, beta)
k=[cos(alpha)*cos(beta);
cos(alpha)*sin(beta);
sin(alpha)];

r{1}=[1/2 -1/2 0];
r{2}=[-1/2 1/2 0];

phi=nan(2,1);

for i=1:2
    phi(i)=2*pi*r{i}*k;
end

Hv=exp(1i*phi);
end